This invention is in the field of vehicle steering and speed sensitive devices to detect a lack of driver alertness and emit a warning thereupon.
Numerous systems are known that sense vehicle steering corrections during a given time period as an indication of driver alertness. One such system is disclosed in U.S. Pat. No. 4,278,969 to Richard Woods, entitled xe2x80x9cDriver Warning Systemxe2x80x9d. The ""969 Woods device incorporates a light source and photocell mounted on the steering column that directs a light beam towards a strip having alternate bands of reflective and non-reflective material. During normal driving patterns, the steering wheel is corrected a given number of times during any predetermined time period. When steering corrections fall below the predetermined number, the driver is usually inattentive due to any of a number of reasons. An audible driver warning system during such conditions has been shown to be effective to arouse the driver to a state of alertness to prevent a vehicle accident. For example, the Woods system is coupled with vehicle speed sensing devices which make it inoperative below a certain vehicle speed so that when the vehicle is parked or moving at a relatively slow speed, the audible alarm will not be sounded even though the necessary steering corrections are not made within the given time period. One significant shortcoming of the Woods device is its reliance on optics for motion detection.
Optical devices used in a motor vehicle environment are subject to significant amounts of dirt, grime, grease and other likely contaminants. Such contaminants will likely interfere with and prevent the Woods device from functioning properly. A steering wheel movement detection device that is unaffected by such contaminants is needed.
A steering wheel movement sensing apparatus for use with a vehicle having a steering shaft, according to one aspect of the present invention, comprises magnetic sensing means for detecting variations in magnetic flux, the magnetic sensing means attached at a fixed location within the vehicle in close proximity to the steering shaft, the magnetic sensing means producing a magnetic signal in accordance with the magnetic flux impinging thereon, a magnetic strip having varying magnetic flux lines, the magnetic strip attached to the steering shaft and in close proximity to the magnetic sensing means so that magnetic flux emanating from the magnetic strip impinge upon the magnetic sensing means, and wherein the magnetic strip moves with respect to the magnetic sensing means when the steering shaft is rotated, circuit means responsive to the magnetic signal for producing an alarm signal in accordance with a lack of deviation in the magnetic signal, and alarm means responsive to the alarm signal for producing an audible sound in accordance with the alarm signal.
One object of the present invention is to provide an improved steering wheel movement detection device.
Another object of the present invention is to provide steering wheel movement detection device that is unaffected by contaminants normally encountered in a motor vehicle environment.
Yet another object of the present invention is to provide a more reliable and more economical steering wheel movement detection device.